Colin Kaepernick (centre) kneels during the national anthem before a game last season.
Photograph: Marcio Jose Sanchez/AP

The latest reason for Colin Kaepernick’s absence from the NFL is apparently not down to his throwing accuracy, his wage demands or his protest against injustice in the United States. Instead, Ray Lewis claims a “racist” tweet sent by his girlfriend Nessa Diab stopped the Baltimore Ravens from signing the quarterback.

Kaepernick attracted huge amount of publicity last season when he refused to stand for the national anthem – which many say has led to his failure to find a new team. The Ravens were said to have been close to signing Kaepernick, but Lewis, the team’s most famous former player, said Diab’s tweet ended that conversation.

“We were going to close the deal to sign him,” Lewis told Showtime’s Inside the NFL on Tuesday night. “[Ravens owner] Steve Bisciotti said: ‘I want to hear Colin Kaepernick speak to let me know that he wants to play football.’ And it never happened because that picture comes up the next day.”

The tweet, from 2 August, compared Lewis and Biscotti to Samuel L Jackson and Leonardo DiCaprio’s characters in Django Unchained. In the film, Jackson plays a loyal slave to DiCaprio’s racist plantation owner. Diab’s tweet was addressed to Lewis and has not been deleted. It was retweeted more than 4,000 times.

Diab, a radio and TV host, is said to have influenced Kaepernick’s stance on social issues. ESPN’s Dianna Russini said John Harbaugh, the Ravens head coach, and general manager Ozzy Newsome were keen on recruiting Kaepernick as a backup to their starting quarterback Joe Flacco, but Bisciotti has blocked the move.

Lewis said: “[Diab] goes out and put out this racist gesture and doesn’t know we are in the back office about to try to get this guy signed. Steve Bisciotti has said it himself: ‘How can you crucify Ray Lewis when Ray Lewis is the one calling for Colin Kaepernick?’”

Kaepernick said he will stand for the anthem this season if he is picked up by a team. He has received support from his fellow quarterbacks: both Aaron Rodgers and Cam Newton believe Kaepernick should be back in the NFL. Rodgers believes the absence is because of his fellow quarterback’s protest.